Although biomineralization in corals has been studied for decades, we cannot yet determine the vulnerability of corals to future scenarios, as the basic mechanism and proteins responsible for the precipitation of the aragonite skeleton remain enigmatic. Recent proteomic analysis has identified a group of coral acid-rich proteins (CARPs) within the protein assemblage that creates a framework for the precipitation of aragonite. To address the questions of how the animal catalyzes the precipitation of biomineral, and the role of individual proteins in the biomineralization reaction in vivo, we propose to study the biological function of the different CARPs in early life stages of diverse corals from sub-tropic, tropic and temperate climates in current and projected ocean acidification conditions. Early stages of biomineralization may be the most susceptible to environmental perturbations. Failure of young corals to biomineralize would compromise recovery from disturbance, dispersal, and sexual reproduction – all with disastrous implications for population dynamics and genetic diversity. The proposed pioneering research aims to test the core hypothesis that stony, symbiotic corals will continue to calcify at projected ocean pH values for 2100. We combine research in coral proteomics and biomineralization, and in larval ecology and developmental biology to lay the foundation for predicting the vulnerability of coral ecosystem diversity and function in the coming decades through unprecedented mechanistic insight. This work will establish new tools and techniques for corals that can transform the researchers’ and community’s mechanistic work in understanding coral physiology, symbiosis, and biomineralization.

Beneficial acclimatization occurs when the environmental signals experienced by the organism modulate their future performance. The capacity for acclimatization in environmentally sensitive organisms, such as reef-building corals, may provide the temporal buffer to increase ecological persistence in a rapidly changing environment. Despite the mounting evidence for beneficial acclimatization, studies of the mechanistic underpinnings (e.g., DNA methylation) are still in their relative infancy, especially in marine invertebrates, like corals.

A combination of global and local stressors threaten the persistence of coral reef ecosystems. Atmospheric CO2 and global mean temperatures are expected to increase significantly. The rapid influx of atmospheric CO2 into the oceans results in ocean acidification (OA), or a shift in the buffering capacity and chemistry of seawater leading to declines in pH and carbonate ions. Together, these stressors are predicted to result in mass coral bleaching, declines in coral calcification of more than 40%, and even extinction. It is thought that the current rate of climate change will outpace the potential for coral reefs to undergo necessary evolutionary adaptation. There is, however, enormous variability in the response of corals to stress and differential survival of species, suggesting that some corals possess mechanisms to better respond to climate change. These mechanisms include innovations related to genetic adaptation, rapid acclimatization through epigenetic mechanisms, and the associated symbiotic communities (Symbiodinium, bacteria, fungi, and viruses). I am currently characterizing the genetic, epigenetic, and symbiotic potential for corals to respond to and resist the adverse effects of increased temperature and OA.

Coral reefs are currently under threat locally, as well as globally from increasing temperature and CO2-induced ocean acidification. While rates of adaptation are anticipated to be slower than climate change, rapid acclimatory processes, such as trans-generational acclimatization and other epigenetic mechanisms may contribute to the maintenance of coral reefs in the future. The goal of this work is to advance our understanding of coral response to climate change. I am focused on testing the effects of increasing temperature and ocean acidification on the corals Pocillopora damicornis and Montipora capitata. These corals provides models to test life-stage specific response and the connection between adults and brooded and spawned larvae in a trans-generational context. This work highlights the necessity of considering rapid acclimatization, or epigenetic processes in our examination of the response of coral to climate change in order to best inform predictions for the future of coral reefs

Marine calcificers are under stress from changing carbonate chemistry in the seawater due to ocean acidification. This is a pressing problems in the shellfish industry, as larval and juvenile shellfish are often extremely sensitive to pH changes causing shell formation and deveopmental issues. To assess the longer term effects and mechanistic underpinnings of biologial response to ocean acidification in an important marine calicifier, I am working with Steven Roberts at UW to examine geoduck response to OA in a series of experiments. Juvenile geoducks were exposed to a three component experiment designed to test for: 1) the effects of acute exposure to ocean acidification, 2) the potential for latent effects due to initial exposure, and 3) the potential for initial exposure to provide preconditioning to secondary exposure. We are examining shell growth to determine organismal performance, as well as DNA methylation and gene expression to determine the link between methylation and plasticity.

Reef-building corals have formed an intimate symbiosis with single-celled endosymbiotic dinoflagellates in the genus Symbiodinium. Here, Symbiodinium photosynthesize and translocate carbon products to the host (e.g., glucose, glycerol, and lipids), along with organic building blocks (amino acids). The cnidarian host, in turn, provides the Symbiodinium nutrients (NH4+, PO4-), metabolic carbon dioxide (CO2) and a physical habitat. There is strong evidence that the differences in Symbiodinium types result in functional differences in coral holobiont performance. Due to these physiological differences, it is posited that symbiotic organisms provide the potential for corals to resist environmental stress. In light of this, it is necessary to assess the diversity and function of Symbiodinium across a wide range of coral-Symbiodinium interactions to determine the potential for changes in symbiont communities to modulate the effects of a changing climate. We are assessing Symbiodinium diversity across a wide range of species and environments using Next Generation Sequencing approaches.

Reponse to Environmental Fluctuations

An organism’s response to the physical environment is determined by its immediate abiotic surroundings, which can have significant spatio-temporal variability. Nonetheless, corals respond in an extremely flexible manner revealing that they are able to acclimatize to thermally heterogeneous environments. The goal of this work is to test the effects of enviornmental fluctuations on organism performance. Our results suggest that reef corals can acclimatize to a variable thermal environment, but also demonstrates that extreme temperature ranges, or prolonged exposure to thermal fluctuations, will result in negative physiological responses. However, these responses may be tempered by plasticity in both the coral host and algal symbiont

ENVIRONMENT

Integrative approach to understanding coral stress responses

I am currently focusing on comparative analyses that simultaneously cross multiple biological scales including the (1) genome, (2) transcriptome, (3) proteome, (4) metabolome, and how they interact to drive (5) phenotype. This work utilizes two coral species (Montipora capitata and Pocillopora damicornis) that are abundant and ecologically important on Hawaiian reefs, and differ in physiological traits and environmental tolerances. We are comparing coral response across scales from physiological to meta-omics under elevated temperature and OA. Together, this holistic, or systems biology approach presents an integrative and comprehensive picture necessary for identification of mechanistic response and specific biological pathways of signal transduction and cellular crosstalk.